1. Field of the Invention
The present invention relates generally to a projection headlamp lighting system and, more particularly, to one using optical light conductors of different diameter sizes having output ends arrayed for projecting an optimum non-symmetric light pattern relative to a vehicle's low beam illumination field.
2. Description of the Prior Art
It is well known that optical light conductors, such as light guide fibers, or fiber optics, may be used efficiently to carry or conduct the output of a light source to various locations without encountering any substantial transmission losses of the light. The light carried by the optical conductors is confined or condensed to the relatively small dimensions of the conductors themselves and is adaptable for use in various related space restrictive applications in automobiles and aircraft or other vehicles concerned with aerodynamic styling and efficiency.
For example, automotive styling must take into account the amount of frontal area necessary to provide the forward illumination needs for the automobile and provide means to reduce that area, and in particular, the height so as to satisfy aerodynamic considerations. The use of optical light conductors that conduct light within small confines are adaptable to these aerodynamic considerations. Further, optical conductors are advantageously adaptable to provide the overall illumination needs of the vehicle.
To reduce overall space requirements for vehicle forward illumination, one known projection headlamp lighting system employs a single light source to generate light, a light distribution arrangement composed of a plurality of optical light conductors to distribute the light to the various lighting positions, and a light projection arrangement composed of optical elements at the lighting positions to receive the light from the optical light conductors and project the light in the desired pattern. This projection headlamp lighting system is disclosed in U.S. Pat. Nos. 4,811,172 and 4,958,263 issued to Davenport et al and assigned to the same assignee as the present invention. The single light source can be of the type described in U.S. Pat. No. 4,958,263. The optical light conductors of the distribution arrangement can be a bundle of optical light guide fibers broken out and distributed as necessary. The light projection arrangement of optical elements can be an array of optical connector, lens, and mask elements as described in U.S. Pat. Nos. 4,868,718 and 4,949,227 issued respectively to Davenport et al and Finch et al and assigned to the same assignee as the present invention. U.S. patent application Ser. No. 07/556,134 filed on July 23, 1990 by Davenport et al and assigned to the same assignee as the present invention discloses an arrangement for disposing a group of different diameter conductors in a housing to achieve a reduced space requirement configuration for the transmission medium. One design objective attained by the present projection lighting system is a substantial reduction in the amount of space needed to achieve proper vehicle forward illumination since there is no longer a need to have individual light source assemblies for up to four light source positions.
However, another design objective which has yet to be achieved is the projection of light on a highway in a manner which utilizes the available light more efficiently. The point of maximum intensity suggested by SAE standards on low beam illumination is at 1.5 degrees down and 2 degrees right from the intersection of horizontal and vertical axes of a reference grid defining a vehicle's forward illumination field. The light projection arrangement of this prior art lighting system projects light in a symmetric pattern about this point of maximum intensity. Thus, some of the projected light must be shielded or masked to block the light from the portion of the illumination field in front of the car where it would glare in the eyes of a driver in an oncoming car. This can result in as much as one-half of the projected light being intercepted and lost.
In order to achieve more efficient utilization of the available light, the necessity to block some of the projected light must be minimized. Therefore, a need exists for a design which avoids the projection of a symmetric light pattern which must be masked to produce the low beam pattern.